Gina

Escape wheel for testing. Thin cord will be wrapped round the boss to drive it. The cord will go over a pulley and over the side of the table to a weight.

Looking more at this design I've seen an improvement that makes it truly deadbeat (no recoil). It is always the leading side of the escape wheel teeth that contacts either ball bearing on the anchor so I was able to make this surface an arc centred on the anchor pivot. Thus in the "lock" phase, the escape wheel doesn't move. Once the pendulum swings back the bearing rolls off the arc and onto the top of the tooth providing the "drive" phase. Once the bearing and tooth part company the escape wheel rotates so that the edge of the tooth near the other ball bearing makes contact with the tooth. The pendulum continues to swing a bit further and the bearing rolls along the tooth front side. It swings outwards and then back (in the "lock" state) until the bearing reaches the slanted top of the tooth and enters the "drive" phase for that side.

Here is my idea for an escapement. It's nearly deadbeat but not quite. The anchor part has "pins" in the form of miniature ball bearings just 6mm OD. These lock the escape wheel on the leading sides of the teeth whilst a sloping top provides the drive action. Having ball bearings rather than plain faces reduces friction.

Having fiddled about with my current anchor escapement including variations in the escape wheel as well as the anchor, with setting it all up then moving it to the clock case and back again after failure, I think it's time to make a test rig! First diagram, new escape wheel and second, a failed idea due to being unable to print sharp teeth. 3D printed plastic (PLA) is very different from brass. Apart from the standard escapements, I have a couple of ideas of my own I can try.

The escapement.

I wondered about the weight of that corrugated roofing but the website says it's lightweight. Actually, rubber roofing is pretty heavy so that stuff could well be lighter than rubber on plywood. Had I found something like that when I built my observatory, I might have used it. Ordinary corrugated galvanised iron sheet was too heavy.

You may be right about OSB - I guess it might fall apart if too thin. I used 11mm OSB on my warm room roof where weight didn't matter. I used 6mm marine ply on the walls and ceiling of my warm room with polystyrene foam slabs in walls and ceiling for insulation. And under the floorboards. No insulation for the scope room.

OSB has a very high weight to strength ratio. If you can avoid walking on it I guess 6mm OSB would suffice but marine play would be better.

What are you putting on top underneath the rubber roofing? I used 6mm marine ply on mine to keep the weight down. It was strong enough for me to walk on and I'm no lightweight!

I can see why you've gone for welded steel tubing James. I imagine that will be a lot lighter than a timber version. Looks good

Photos of the latches on the observatory.

I think these were the ones. Large Heavy Duty Over Centre Catch Toggle Clamp Latch Trailer Door Lock Here'a a photo from my backup drive.

I'll see if I can find the latches I used. Think I got them from Amazon. They were like these but much heavier duty.

Absolutely Kev. Roof is now equipped with super-strong lockdown hasps which are engaged whenever I close the roof. They stop the roof being blown open or closed when engaged too. The roof runs well and just a strong breeze is enough to propel the roof on its tracks.

I like your anti-lift system Kev. I would have done the same when I built mine if I'd thought of it! Would have saved retrieving the roof from the fence 20 yards away and getting my neighbours to put it back on the main body of the observatory after I had repaired it. Three strong young men did the job.

Now to the fly-fan gear chain, taking what I have drawn above :- Gear on main shaft - 105mm with 75mm forming the pair - ratio 105:75 = 7: 5 Next gear pair to fly-fan - 150:20 = 15:2 Total ratio = 15x7/(5x2) = 21:2 or a little over 10:1 making the fly-fan rotate at 10x the striking rate With a striking rate of one per second the fly-fan wants to rotate at 10.5rps which from hand testing seems a good starting point.

I think I might just have managed to fit all the clock and striking system parts in, provided I change to a different auto-wind for the striking system. I thinking of using a single chain or maybe cord and winding up on a ratchet every so often with a motor. Not as nice as a continuously running auto-winding (like the clock) but if needs must... Some calculations :- Gear ratio - main strike shaft to gear on MH axle = 180:30 = 6:1. Next is 160:80 = 2:1 and the ratio of gear to drum is the same giving another 2:1. Total ratio is 24:1. Over a 12 hour period there are 78 strikes and 78 revolutions of the main striking axle. 78/24 = 3.25. Circumference of drum = 80xPi = 251mm approx. Drop in 12 hours would be 3.25x251 = 817 approx. Without a doubling up pulley the drop is 1.5m which would be adequate for winding twice a day. If winding were limited to once a day a pulley would be required.

Can't remember how I did mine now but it will be in one of my observatory building threads - go back around 6 years or so...

This photo shows a possible arrangement for the hour drive gears and rack & cam for the striking mechanism. The hour and strike parts are test pieces using some cheap ABS filament. Only the first pair of hour train gears are shown and only part of the striking mechanism - there's also the gear train and the parts that start the striking controlled by the minutes (so that it strikes exactly on the hour).

Fitting everything in is mighty difficult. The gears that drive the hour wheel have to be on the left as there is no room on the right. This causes conflict with the striking gear chain and chain sprocket. Both chains have to go between the two acrylic plates for the weights to fit in the trunk and not collide with the pendulum.

Photo of gear train.

Yes, I added my own cooling to the ZWO camera I used in my all sky camera.

Have a look here :- ZWO CMOS astro cameras at FLO

Almost stopped raining here now... Very heavy rain earlier!

Most DSLRs are not really suitable for conversion as cooling is usually not very effective once you get down to freezing. As Louise says, with the advent of relatively cheap CMOS astro cameras it's really not worth it. I spent well over £1000 trying before these cheapish astro cameras came out. It was a very frustrating exercise - I have a large graveyard of dead DSLRs!! I will try anything but that was really not going anywhere. (Except for emptying the bank balance even with cameras off ebay costing just a few tens of pounds.)